Immunogenicity and safety of a DTaP-IPV/Hib pentavalent vaccine given as primary and booster vaccinations in healthy infants and toddlers in Japan

[[[ Background: ]]] Globally, the use of single DTaP-IPV/Hib vaccines that combine DTaP-IPV and Hib is widespread, but in Japan vaccination is usually concomitant at separate sites. The immunogenicity and safety of a primary vaccination series and booster of a combined pentavalent DTaP-IPV/Hib vaccine were evaluated and compared to separate administration of DTaP-IPV and Hib in Japanese infants. [[[ Methods: ]]] Healthy Japanese infants were administered DTaP-IPV/Hib (Group A: N = 207) or DTaP-IPV + Hib (Group B: N = 207) by the subcutaneous (SC) or DTaP-IPV/Hib by the intramuscular (IM) route (Group C: N = 10). All subjects received a 3-dose primary vaccination series and a booster. Non-inferiority (Group A versus Group B) was tested post-primary series and subsequent post hoc analyses were performed for anti-Hib. Safety was assessed by parental reports. [[[ Results: ]]] Non-inferiority for SC administration of Group A versus Group B for the primary series was demonstrated for antibody responses to all antigens except Hib using the threshold of 1.0 μg/mL. Post hoc analyses for anti-Hib demonstrated non-inferiority for the primary series response using 0.15 μg/mL, and for pre-booster antibody persistence and the booster response using 0.15 μg/mL and 1.0 μg/mL. The immune response was similar for each antigen following SC or IM administration. There were no safety concerns in any group, and a lower incidence of injection sites for the IM route was observed as expected. [[[ Conclusions: ]]] These data show the good immunogenicity and safety profile of the DTaP-IPV/Hib vaccine as a 3-dose infant primary series followed by a booster in the second year of life in Japan.